Recommendations for Calorifiers with Large Bore Connectors on Heating Circuit.

[alan_fincher]

I think we will be looking to replace the hot water system on "Flamingo".

 

We have an air cooled engine, so can only heat a calorifier by boilers or back boilers, and my current focus would be to try and actually extract heat properly from the large Much Wenlock stove with back boiler, already in the boat, (the current system struggles, despite being pumped).

 

I would much prefer to try and heat water by a gravity thermosyphon arrangement, and not to have to rely on pumping, at least for this bit of the installation. I think I can get calorifier and stove very close together, which should help.

However the majority of marine calorifiers sold for canal boat use seem to expect a pumped circuit, and often have only 1/2" BSP or 1/2" barbed connectors for the coils. (The size of the internal coils themselves often not being quoted). This seems far too small for a gravity circuit, to me.

 

I can find a few that seem to use 3/4" BSP connectors, and sometimes the internal coil is confirmed as 22mm, which seems more consistent with a gravity circuit. I assume the bigger the better.

 

However those I have quickly found even more prohibitively expensive than most calorifiers already are!

 

So has anybody managed to purchase a calorifier suitable for thermosyphoning with a large back boiler stove, and if so how successful has the installation been please?

 

I would appreciate recommendations for likely suppliers.

 

I would also be keen to hear of any difficulties people have encountered.

[magnetman]

Didn't someone do a heat exchanger on an air cooled Lister? Possibly lagging the exhaust with copper tube then pump water round it.

May be confused but there must be an opportunity there

 

As for the calorifier I did once buy a twin coil from Uxbridge with a normal 15mm coil and a 22mm coil for a Rayburn installation I fitted myself, with a full thermosyphon system. It was perfectly effective. It was also expensive. 60 litres iirc. Rayburns do have big boilers...

[BEngo]

You will only want a single coil calorifier, so the easiest and cheapest way is to use a domestic calorifier/hot water cylinder, as these come with large bore coils. You must fit a separate pressure switch to the fresh water pump(s) and set it so that the max working pressure of the cylinder is not exceeded.

 

RS do, or did, an adjustable pressure switch which can be calibrated off the accumulator or there is always the Square D pressure switch if you are feeling wealthy, which as an old boat owner you must be (.

 

N

[magnetman]

My calorifier was a vertical unit about 20ft from the Rayburn, with 28mm primary circulation passing a few inches from the calorifier before stepping down to the calorifier fitting size.

 

The primary circuit was all 28mm, being tapped into rather than plumbed directly through tanks or radiators.

[BargeeSpud]

I have got a 70 litre (approx) vertical calorifier with a 22mm gravity coil in it & it didn't cost the earth, in fact it was cheaper than a standard 55 litre calorifier from the usual sources. It seems to work very well, but I'm afraid I don't know who made it & the guy who fitted it for me flat refused to tell me! I guess to protect his supply chain. I can only assume the maker is not connected to the marine industry, but the calorifier is identical in every way with a marine version, so if he is, then I've been supplied direct.

 

Sorry I can't be more helpful.

[ditchcrawler]

I think we will be looking to replace the hot water system on "Flamingo".

 

We have an air cooled engine, so can only heat a calorifier by boilers or back boilers, and my current focus would be to try and actually extract heat properly from the large Much Wenlock stove with back boiler, already in the boat, (the current system struggles, despite being pumped).

 

I would much prefer to try and heat water by a gravity thermosyphon arrangement, and not to have to rely on pumping, at least for this bit of the installation. I think I can get calorifier and stove very close together, which should help.

 

However the majority of marine calorifiers sold for canal boat use seem to expect a pumped circuit, and often have only 1/2" BSP or 1/2" barbed connectors for the coils. (The size of the internal coils themselves often not being quoted). This seems far too small for a gravity circuit, to me.

 

I can find a few that seem to use 3/4" BSP connectors, and sometimes the internal coil is confirmed as 22mm, which seems more consistent with a gravity circuit. I assume the bigger the better.

 

However those I have quickly found even more prohibitively expensive than most calorifiers already are!

 

So has anybody managed to purchase a calorifier suitable for thermosyphoning with a large back boiler stove, and if so how successful has the installation been please?

 

I would appreciate recommendations for likely suppliers.

 

I would also be keen to hear of any difficulties people have encountered.

I got mine from Calcutt with 22mm coils but it was a few years back

[smileypete]

Gotta watch for reverse thermosyphoning, was a fairly recent topic on it.

 

A google search will turn up a few manufacturers, like Albion, McDonald, Newark:

 

https://duckduckgo.com/?q=custom+marine+calorifiers

 

Seems to me most problems happen with a fully pumped or sometimes a fully gravity system, so why not use a hybrid of the best of both?

 

cheers, Pete.

~smpt~

Edited January 2, 2015 by smileypete

[ditchcrawler]

You will only want a single coil calorifier, so the easiest and cheapest way is to use a domestic calorifier/hot water cylinder, as these come with large bore coils. You must fit a separate pressure switch to the fresh water pump(s) and set it so that the max working pressure of the cylinder is not exceeded.

 

RS do, or did, an adjustable pressure switch which can be calibrated off the accumulator or there is always the Square D pressure switch if you are feeling wealthy, which as an old boat owner you must be (.

 

N

I have a square D switch and wouldn't be happy trying to calibrate that to ½ Bar

[smileypete]

I have a square D switch and wouldn't be happy trying to calibrate that to ½ Bar

 

Could handle that with a pressure reducing valve, but a bigger problem might be finding a PRV below 1 bar.

 

Another problem may be that the guarantee doesn't cover any kind of unvented use.

 

cheers, Pete.

~smpt~

Edited January 2, 2015 by smileypete

[alan_fincher]

OK, so how practical is it to use a normal domestic cylinder in a boat installation, then? I thought it had been suggested on the forum regularly that it is not a great idea, and presumably there is a reason why people pay the considerable excess cost of a marine calorifier over a normal domestic hot water cylinder.

 

Having a very quick "Google", I can quickly turn up domestic cylinders specified to a wide range of maximum heads, such as 10 metres and 25 metres.

 

10 metres is less than 1 bar, by my calculation or about 14psi, so I would have thought most unsuitable A limit of 25 metres head raises this to a number that is still below 2.5 bar, or 35 psi - clearly a pressure that can be exceeded by some boat water pumps, if not tightly calibrated and controlled.

 

So what is the minimum spec a domestic cylinder would need to comply with to be used on a boat, even if you use an external pressure switch that is not the one in the pump?

[smileypete]

Are you planning to run the stove all the time when occupied in winter? Or raise the cylinder so the coil is above the backboiler and rads?

 

cheers, Pete.

~smpt~

[Detling]

Have you thought of using both coils in parallel in a twin coil calorifier, it won't give you a 25mm bore but it will give 22mm, if both are 15mm.

[alan_fincher]

Have you thought of using both coils in parallel in a twin coil calorifier, it won't give you a 25mm bore but it will give 22mm, if both are 15mm.

 

No, but you have made me think about it now!

[David Mack]

A few years ago I had a domestic hot water cylinder made to measure to a non-standard size by Gledhill . It was to replace an existing cylinder which had sprung a leak, and I didn't want to change the pipework and the cupboard around it. In particular, they were able to fit 1 1/4" bsp fittings, rather than the normal 1" or 3/4". In the end it was actually a little cheaper than the nearest standard size from my local plumbers merchant, and was delivered in a matter of days.

 

The cylinder they supplied was specifically noted as suitable only for an open-vented system, and not for a pressurised system, but they also make other types. They were helpful on the phone , so I would recommend having a chat to them. In fact my only complaint was that their delivery driver drove across my front lawn rather than reversing out or doing a three point turn on the driveway!

[alan_fincher]

In case it is useful information to anybody else in future, I have finally sourced and installed a new calorifier specifically made with a large bore coil. in the hope it may be possible to make the circuit thermo-syphon without a pump.

Mine came from Copper Cylinder supplies, although they are actually manufactured by Mannley Cylinders in West Yorkshire, who seem to be their own "own band" company.

You can specify exactly what you want, including where all the ports and the immersion will be, and they make it to order. (I specified extra insulation, as an option, for example).

I found them very efficient and helpful, and was staggered that I could tell them what I wanted made one afternoon, and it arrived with me in the morning 2 days later.

Not hugely more expensive than off the shelf offerings, and massively cheaper than a quote I got from Surejust/Surecal, (who also had a lad time of over 2 weeks).

At the moment it has gone into a circuit that is still pumped, but as and when I get things to the state to try without a pump, I will report back on success or failure of that.

 

[smileypete]

38 minutes ago, alan_fincher said:

At the moment it has gone into a circuit that is still pumped, but as and when I get things to the state to try without a pump, I will report back on success or failure of that.

Might want the entirety of the calorifier coil at a level above the top outlet of the backboiler.

Otherwise when the stove goes out the thermosyphon will work in reverse, cooling the calorifier and sending heat up the stove flue.

If the stove tends to run 24/7 or the hot water gets used before the stove goes out, I s'pose it should be OK.

Edited November 17, 2017 by smileypete

[Jen-in-Wellies]

I've got a successful thermosyphon system on my boat. Squirrel stove, with a vertical twin coil cauliflower in a cuboard beside it. No problem finding one with a 3/4 BSP fittings and 22mm internal coil. The other coil is used for solar hot water in the summer, but that is another story.

The calorifier is raised up high so the lower end of the 22mm coil is at gunwhale level. The pipe then runs through fin rads at this level before turning 180 degrees and returning about 6" lower down. All done in 28mm pipe stepping down to 22mm for the calorifier and finrads. No reverse syphoning due to the height the calorifer is installed at. Very peaceful with no pump noise.

Jen

[rusty69]

21 minutes ago, Jen-in-Wellies said:

Squirrel stove, with a vertical twin coil cauliflower in a cuboard beside it.

Can I sleep in your cauliflower cupboard please, its freezing here!

[Jen-in-Wellies]

1 hour ago, rusty69 said:

Can I sleep in your cauliflower cupboard please, its freezing here!

Not when I've got bread rising in there!